CEH Enumeration and System Hacking Practice Question
This CEH practice question tests your understanding of enumeration and system hacking. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A security auditor runs SNMPwalk against a network device using the default community string 'public' and obtains extensive system information. Which THREE of the following are effective countermeasures to prevent unauthorized SNMP enumeration?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Implement an access control list (ACL) limiting SNMP access to management hosts
Options A, C, and D are correct. Changing default community strings is a basic step. Using SNMPv3 provides encryption and authentication. Restricting SNMP access to specific IP addresses reduces exposure. B and E are incorrect as they increase risk or are unrelated.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Disable SNMP entirely on all devices
Why it's wrong here
While effective, this may break legitimate monitoring; it is not always practical.
✓
Implement an access control list (ACL) limiting SNMP access to management hosts
Why this is correct
ACLs restrict which IPs can query SNMP, reducing exposure.
Related concept
Standard ACLs match source addresses.
✗
Set the community string to 'private' for read-only access
Why it's wrong here
'private' is also a default community string and should not be used.
✓
Change the community string from 'public' to a complex string
Why this is correct
Default community strings are well-known; changing them prevents trivial enumeration.
Related concept
Standard ACLs match source addresses.
✓
Upgrade SNMP to version 3 with authentication and encryption
Why this is correct
SNMPv3 provides security features that prevent unauthorized access.
Related concept
Standard ACLs match source addresses.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related CEH ACL questions on filtering logic and placement.
Enumeration and System Hacking — This question tests Enumeration and System Hacking — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Implement an access control list (ACL) limiting SNMP access to management hosts — Options A, C, and D are correct. Changing default community strings is a basic step. Using SNMPv3 provides encryption and authentication. Restricting SNMP access to specific IP addresses reduces exposure. B and E are incorrect as they increase risk or are unrelated.
What should I do if I get this CEH question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related CEH ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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